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6.13 Heat recovery
FHW
F
T
T
T
T
HR1I
HR1O
3W
HRI
T
T
HR1
disch
pRack pR300T manages up to two heat recovery functions at the same
time. The related parameters can be set from the main menu, branch
E.e.a.b.01.
Activation and control of each heat recovery function will refl ect the
percentage of heat demand calculated based on one of the following:
•
digital input
•
temperature probe
•
external analogue signal
In the last two cases, a digital input can still be used to enable the function.
Once active, heat recovery control can act on the HPV valve set point and
on the eff ective Gas Cooler set point, in both simultaneous mode (acting
on both at the same time) and in sequential mode, based on thresholds
(fi rst acting on the HPV and then the Gas Cooler, when exceeding a
certain heat demand threshold):
•
action on HPV set point (in barg/psig)
•
action on GC set point °C/°F)
When acting on the HPV valve set point, the heat recovery function
modifi es the "Minimum HPV valve control set point" parameter (screen
Eib28), whose default value is 40.0 barg and used as a lower limit for
calculating the dynamic pressure set point for controlling the high
pressure valve.
Increasing this minimum set point from its default value (40.0 barg) to a
new minimum set point (e.g. 75.0 barg) causes the system to operate in
transcritical conditions, even when the Gas Cooler outlet temperature is
between Tmin and T23 (see the control parameters, screen Eib05); in this
zone, defi ned as subcritical, the HPV set point would be calculated based
on subcooling.
This minimum set point can be increased further (screen Eeab28) in
proportion to the heat recovery demand, up to a settable maximum limit
value (e.g. 85.0 barg).
Copyright HPL March 2021
FHW
F
T
T
T
T
HR2I
HR2O
3W
HR2
T
T
HR2
disch HR2
Fig. 6.ap
3W
GC
T
T
GAS cooler
ING GC
If the HPV valve set point calculated based on the Gas Cooler temperature
exceeds the minimum set point modifi ed by the heat recovery function,
the controller will use the calculated set point.
Request (%)
100%
Min. request
activation
0%
Status (0-1)
1
0
Pressure
(barg)
85.0 barg Max HPV
set point (heat
recovery ON)
75.0 barg Min HPV
set point (heat
recovery ON)
40.0 barg Min HPV
set point (heat
recovery OFF)
(*) Different activation's delays are not considered in this graph
When acting on the on the Gas Cooler set point, the Gas Cooler fan
temperature set point can be increased gradually to the maximum limit.
This limit is equal to the maximum allowable set point (screen Dab06)
when operating in simultaneous mode, or the value set on screen Eeab29
in sequential mode.
In simultaneous mode, the increase will start at the same time as the
action on the HPV valve set point, while in sequential mode the increase
will start after having exceeded a settable heat demand percentage limit
threshold (Eeab29).
If the fl oating condensing function is active (branch D.a.d), this can be
disabled when heat recovery is active (Eeab04), however if it is enabled
while heat recovery is active, the Gas Cooler set point increase can be
added directly to the outside temperature.
47
Page 96 of 169
T
T
P
GC
GC by passed
GC
T
T
P
Time
Fig. 6.aq
P4367 Rev 01
pRack PR300T +0300018EN rel. 1.5 - 02.05.2017
ENG
HPV
ExV
Heat
recovery
request
Heat
recovery
status
Min.
set-point
HPV
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